One method of controlling the casting process has been the use of an induced electromagnetic field, rather than a mold with definite walls, to both confine and shape the molten metal or alloy which is being cast. This process utilizes a strong electromagnetic field to counterbalance the metallostatic forces effected by the head of molten metal or alloy.
It has generally been necessary to employ relatively low heads of pressure in the molten metal to minimize the power requirements of the electromagnetic field utilized in such a process. Molten metal or alloy head height thus becomes an important parameter to measure, as does any change in head height during an electromagnetic casting run. In addition, metal or alloy head control in such a process should be sufficiently precise to minimize fluctuations in the metallostatic forces and prevent surges of high velocity molten metal streams within the casting. It thus often becomes essential to know the precise location of the metal head top surface at any given instant during an electromagnetic casting run, and to be able to continuously monitor such location during the electromagnetic casting run thereby enabling adjustment of the casting system.